Method for forming fluoride spray coating, and fluoride spray coating covered member

ABSTRACT

[Problem] To provide a fluoride spray coating covered member in which a fluoride spray coating firmly adheres by coating carbide cermet to a surface of a substrate and interposing it, and to propose a method therefor. [Solution] A fluoride spray coating is formed in such a manner that an undercoat layer of carbide cermet, which covers a substrate in a film-shaped manner while a tip portion of carbide cermet particles is embedded in the substrate, or a primer part of carbide cermet, is formed by blowing a carbide cermet material at a high velocity by using a spray gun to a surface of the substrate, and after that, a fluoride particle is sprayed thereon.

TECHNICAL FIELD

This invention relates to a method for forming fluoride spray coatingand a fluoride spray coating covered member. More particularly, theinvention relates to a method for forming a fluoride spray coating on asurface of a member for semiconductor working device and the likesubjected to a plasma etching process under highly corrosive gasenvironment through carbide cermet, and also relates to a fluoride spraycoating covered member provided by performing this method.

RELATED ART

As a coating with corrosion resistance formed on a surface of the memberfor semiconductor working device, a spray coating is useful. Forexample, in case that the member is subjected to a plasma treatmentunder an existence of halogen or halogen compound, or in case that themember is used in a field of semiconductor working device wherein fineparticles generated by the plasma treatment are required to be cleanedand removed, it is necessary to apply a further surface treatment, andthus there are proposed several conventional techniques.

In a working environment of the devices such as dry etcher, CVD and PVDused in the semiconductor working process and the production process ofliquid crystal, a higher cleanliness is demanded so as to improve anaccuracy of micro-fabrication associated with high circuit integrationof a substrate such as silicon and glass. However, since gas or aqueoussolution having a strong corrosive nature such as fluoride and chlorideis used in various processes for micro-fabrication, the members providedin these devices are fast in corrosive wearing, and as a results, thereis a fear of secondary contamination of environment based on thegeneration of corrosion products.

The manufacturing and working process of the semiconductor device is aso-called dry process in which a compound semiconductor made Si, Ga, As,P and so on is mainly used and treated in vacuum or in an atmosphereunder a reduced pressure. As an apparatus and a member used in the dryprocess are included an oxidation furnace, CVD apparatus, PVD apparatus,an epitaxial growing apparatus, an ion implantation apparatus, adiffusion furnace, a reactive ion etching apparatus as well as membersand parts accompanied with these apparatuses such as pipes, intake andexhaust fans, vacuum pump, valves and the like. In addition, it is knownthat the apparatus uses fluorides such as BF₃, PF₃, PF₆, NF₃, WF₃, HF,chlorides such as BCl₃, PCl₃, PCl₅, POCl₃, AsCl₃, SnCl₄, TiCl₄, SiH₂Cl₂,SiCl₄, HCl, Cl₂, bromides such as HBr, and further strong corrosivereagents and gases such as NH₃, CH₃F or the like.

In the dry process using these halides, plasma (low-temperature plasma)is frequently used for activation of reaction and the improvement ofworking accuracy. Under an environment using such plasma, varioushalides are converted into strong corrosive atomic or ionized F, Cl, Br,l, and provide a large effect to micro-fabrication of semiconductormaterial. On the other hand, there is a problem that fine particles ofSiO₂, Si₃N₄, Si, W and the like, which are removed from the surface ofthe plasma-treated semiconductor material (especially a plasma etchingtreatment) through the etching treatment are floated in the treatingenvironment and adhered to the surface of the device during or after theworking to considerably deteriorate the quality thereof.

As one of these countermeasures for these problems, there is a methodwherein the surface of the member for semiconductor manufacturing andworking apparatus is subjected to a surface treatment with an anodeoxide of aluminum (alumite). And also, there is known a techniquewherein an oxide such as Al₂O₃, Al₂O₃.Ti₂O₃, Y₂O₃ or an oxide in GroupIIIa metal of the Periodic Table is applied onto a surface of the memberby a spraying method or an evaporation method (CVD method, PVD method),or utilized as a sintered body (Patent Documents 1-5).

In recent years, there is known a technique wherein the resistance toplasma erosion is improved by irradiating a laser beam or an electronbeam onto a surface of Y₂O₃ or Y₂O₃—Al₂O₃ spray coating to remelt thesurface of the spray coating (Patent Documents 6-9).

Moreover, in a field of high-performance semiconductor processing, thereis a proposal that YF₃ (yttrium fluoride) is used in a coating-formationcondition as a means for improving a cleanness of working environment aswell as a material for surpassing plasma erosion resistance of Y₂O₃spray coating. For example, there are proposed a method of covering asurface of a sintered body of YAG or the like or an oxide in Group IIIaelement of the Periodic Table with YF₃ coating (Patent Documents 10˜11),a method wherein a mixture of Y₂O₃ or Yb₂O₃ and YF₃ and the like is usedas a coating material (Patent Documents 12-13), a method in which YF₃itself is coated as a coating material by a spraying method (PatentDocuments 14-15).

PRIOR ART DOCUMENTS Patent Documents

-   Patent Document 1: JP-A-H06-36583-   Patent Document 2: JP-A-H09-69554-   Patent Document 3: JP-A-2001-164354-   Patent Document 4: JP-A-H11-80925-   Patent Document 5: JP-A-2007-107100-   Patent Document 6: JP-A-2005-256093-   Patent Document 7: JP-A-2005-256098-   Patent Document 8: JP-A-2006-118053-   Patent Document 9: JP-A-2007-217779-   Patent Document 10: JP-A-2002-293630-   Patent Document 11: JP-A-2002-252209-   Patent Document 12: JP-A-2008-98660-   Patent Document 13: JP-A-2005-243988-   Patent Document 14: JP-A-2004-197181-   Patent Document 15: JP-A-2002-037683-   Patent Document 16: JP-A-2007-115973-   Patent Document 17: JP-A-2007-138288-   Patent Document 18: JP-A-2007-308794

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

A fluoride spray coating has an excellent halogen resistance but has adrawback that an adhesion with substrate is worse. From an experience ofthe inventors, since a fluoride spray coating covered to a substratesurface has a less ductility and a small surface energy, there is aphenomenon that a crack is generated and a local peeling-off occurs.However, a countermeasure for eliminating the above drawback is notreferred in any of the above Patent Documents. This cause is assumed tobe the followings. That is, since fluoride (YF₃, AlF₃ and the like) isnot thought to be adapted to Japanese Industrial Standards (JIS) andInternational Organization for Standardization (ISO) that are a basis ofa spray and working technique, a working standard method for a fluoridespray coating is not defined, and thus a spraying is performed on thebasis of the same standard as that of metal (alloy), ceramics and cermetmaterial and the like.

In the spray working, a substrate surface is generally subjected to aroughening before the spray working. In the Japanese IndustrialStandards (JIS), the following blast roughening treatment methods aredefined for each of coating materials.

(1) Metal coating: In JIS H8300 “Thermal spraying of zinc, aluminum andalloy thereof—Thermal spray working standard”, oxide is removed from asteel substrate by using blast-furnace slag, steel slag and the likedefined by JIS Z0312 for oxide (scale) removal, and then the oxideremoved surface is subjected to a roughening treatment by using acast-iron grid defined by JIS Z0311 or a fused alumina (Al₂O₃) griddefined by JIS Z0312.

(2) Ceramic coating: In JIS H9302 “Ceramic thermal spray workingstandard”, after the blast treatment for removing the oxide isperformed, the treated surface is subjected to a roughening treatment byartificial abrasives (Al₂O₃, SiC) defined by JIS R6111.

(3) Cermet coating: In JIS H8306 “Cermet thermal spraying”, it isdefined that a roughening treatment is conducted by using the cast-irongrid manufactured in accordance with JIS G5903 or the artificialabrasives manufactured in accordance with JIS R6111.

As mentioned above, in the thermal spraying field, the blast materialsused for the blast roughening treatment to the substrate surface and itsroughened condition are severely defined for each of the coatingmaterials. Moreover, as for the substrate roughening treatment disclosedin each of the Patent Documents relating to the fluoride spray coating,a treatment condition and an extent of roughening are not disclosed.Even if it is disclosed, only the blast material is disclosed, and it isnot a disclosure of a method for improving an adhesion of the fluoridespray coating (Patent Documents 14, 16). In Patent Documents 17, 18, aroughening by corundum (Al₂O₃) is only disclosed. In fact, in thesePatent Documents and known documents relating to the fluoride spraycoating, there is no disclosure about a roughening treatment as acountermeasure for improving an adhesion of the coating and a formationof an intermediate layer such as an undercoat layer, and also there isno disclosure about a surface roughness.

Further, in these Patent Documents, a process for forming the fluoridespray coating directly onto the substrate surface is employed, and thereis no ingenuity for an adhesion of the fluoride spray coating, forexample, there is no intermediate layer such as the undercoat layerformed prior to a formation of the fluoride spray coating. This isassumed as a cause for frequently generating a peel-off of the coatingunder an actual use environment.

An object of this invention is to provide a fluoride spray coatingcovered member which a firm adhesion of a fluoride spray coating isperformed by interposing carbide cermet on a substrate surface, and itsadvantageous manufacturing method.

Solution for Problems

This invention found out that an employ of new spray coating formationtechniques from the following viewpoints is advantageous so as toovercome the above problems that the conventional technique has.

(1) In order to improve an adhesion property of a fluoride spraycoating, a preliminary treatment technique of a substrate surface isimportant. Particularly, prior to forming a fluoride spray coating ontothe substrate surface, it is effective to form an intermediate layer(preliminary treatment) such as an undercoat layer of carbide cermet ora primer part in which carbide cermet particle is stuck as piles and issparsely scattered on the substrate surface. Since the intermediatelayer of carbide cermet formed by this preliminary treatment has a goodmatch with a fluoride (between fluorine and carbon), it is beneficialfor increasing adhesion strength of a fluoride spray coating as atopcoat.

(2) As one of the above preliminary treatments, an undercoat layer isformed onto the roughened substrate surface after a blast treatment by ahigh velocity spraying of carbide cermet. In this case, after forming astate such that a part of primary particles blown to the substratesurface is stuck as piles to the substrate surface and is upstanding, acoating-formation is performed by repeating the blowing treatmentsuccessively. After that, it is advantageous to form a fluoride spraycoating according to a conventional means on the undercoat layer formedin a film-shaped manner.

(3) Moreover, as another preliminary treatment, after forming a non-filmshaped primer part (adhesion area ratio: about 8-50%) wherein a carbidecermet particle is stuck as piles and is sparsely upstanding to thesubstrate surface by blowing a carbide cermet material at high velocity(150-600 m/sec.) in addition to a roughening of the substrate surface bya blast treatment, it is advantageous to improve an adhesion property ofa fluoride spray coating by forming a fluoride spray coating through aprimer part.

(4) In this case, prior to a formation of the undercoat layer or theprimer part of carbide cermet, it is advantageous to perform a blastroughening treatment using particles such as Al₂O₃ and SiC to thesubstrate surface, which is compliant with a ceramic spray coatingworking standard defined by JIS H9302.

(5) Basically, after roughening the substrate surface by a blasttreatment, the non-film shaped primer part having a structure that atleast a part of the tip portion of carbide cermet spray particles flyingat a high velocity is stuck as piles and is sparsely upstanding to thesubstrate surface, is formed by blowing a carbide cermet material suchas WC—Co and WC—Ni—Cr at a high velocity (spraying number: not more than5 times) by means of a spray gun used in a high-velocity flame sprayingmethod or a low-temperature thermal spraying method. Then, it ispreferable to form the film-shaped undercoat layer wherein carbidecermet spray particles are deposited by repeating this statesuccessively (spraying number: not less than 6 times). Then, a fluoridespray coating is formed by a conventional spraying method using a plasmaflame or a combustion flame of fossil fuel as a heat source through suchan intermediate layer (primer part or undercoat layer).

(6) After forming the intermediate layer (primer part and undercoatlayer) by spraying successively a carbide cermet material at a highvelocity to the substrate surface to which a roughening treatment isperformed, it is preferable to preheat the substrate at a temperature of80° C.-700° C. and then to perform a spraying of a fluoride spraymaterial by means of methods such as atmospheric plasma spraying method,reduced-pressure plasma spraying method and high-velocity flame sprayingmethod.

The invention developed according to the above viewpoints is a methodfor forming a fluoride spray coating characterized in that an undercoatlayer of carbide cermet, which covers a substrate in a film-shapedmanner while a tip portion of carbide cermet particles is embedded inthe substrate, or a non-film shaped primer part of carbide cermet, isformed by spraying a carbide cermet material by using a spray gun for ahigh velocity spraying to a surface of the substrate to which aroughening treatment is performed, and after that, a fluoride spraycoating material is sprayed onto the undercoat layer or the primer part.

Moreover, the invention proposes a fluoride spray coating covered membercomprising: a substrate, a surface of which is subjected to a rougheningtreatment; a carbide cermet layer coated to a surface of the substrate;and a fluoride spray coating formed thereon, characterized in that thecarbide cermet layer is a film-shaped undercoat layer wherein a part ofcarbide cermet particles is embedded in the substrate to make athickness thicker or a primer part of non-film shaped structure having aconstruction that a tip portion of spray particles is stuck as piles andis sparsely upstanding, by blowing carbide cermet particles having aparticle size of 5-80 μm which is made of one or more metal carbidesselected from Ti, Zr, Hf, V, Nb, Cr, Mn, W and Si and 5-40 mass % of oneor more metals or alloys thereof selected from Co, Ni, Cr, Al and Mo byusing the spray gun for a high velocity spraying.

In addition, in the invention the following constructions are preferablesolution means:

(1) The undercoat layer of carbide cermet is a layer with a film-shapedstructure having a layer thickness of 10 μm-150 μm, in which, at a sideof a substrate surface, a tip portion of a part of the carbide cermetparticles is embedded in the substrate and a thickness is made thickerby increasing a spraying number;(2) The primer part of carbide cermet is made by a non-film shapedstructure having such a state that a tip portion of spray particles isstuck as piles and is sparsely upstanding, at a portion of area ratio8-50% with respect to a substrate surface;(3) The undercoat layer and the primer part of carbide cermet are formedin such a manner that a spray treatment, in which particles having aparticle size of 5-80 μm which is made of one or more metal carbidesselected from Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W and Si and 5-40 mass % ofone or more metals or its alloys selected from Co, Ni, Cr, Al and Mo aresprayed by using the spray gun for a high velocity spraying at a flyingvelocity of 150-600 m/sec., is repeated at 6 times or more in case ofthe undercoat layer and at 5 times or less in case of the primer part;(4) The substrate is preheated to 80-700° C. prior to a spraying offluoride particles;(5) A spray method of fluoride is any one spray method selected fromatmospheric plasma spraying method, reduced-pressure plasma sprayingmethod and high-velocity flame spraying method;(6) Any of Al and its alloy, Ti and its alloy, carbon steel, stainlesssteel, Ni and its alloy, oxide, nitride, carbide, silicide, carbonsintered body and plastics, a surface roughness of which is controlledto be Ra: 0.05-0.74 μm and Rz: 0.09-2.0 μm by a blast rougheningtreatment in which abrasives such as Al₂O₃ and SiC are blown, is used asthe substrate;(7) The fluoride spray coating is formed in such a manner that fluorideparticles having a particle size of 5 μm-80 μm made of a fluoride of oneor more materials selected from a group of: Mg in Group IIa of thePeriodic Table; Al in Group IIIb of the Periodic Table; Y in Group IIIaof the Periodic Table; and lanthanide metals of Atomic Numbers 57-71 inthe Periodic Table such as La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho,Er, Tm, Yb and Lu are blown to the substrate surface to be a coatingthickness of 20 μm-500 μm; and(8) The fluoride spray coating has a thickness of 20-500 μm.

Effect of the Invention

According to the invention having the above constructions, the followingeffects will be expected.

(1) If a hard carbide cermet material is blown to a substrate surface ata high velocity, at least a part of primary carbide cermet sprayparticles is stuck to the substrate surface, and then a thicknessbecomes gradually thicker by a repetition of sprayings to form anundercoat layer or the primer part. If fluoride particles are sprayed tothe thus formed undercoat layer or primer part, the fluoride sprayparticles adhere onto the undercoat layer of carbide cermet with a highadhesion.(2) Particularly, a fluoride has a weak chemical wettability and lessjoining property with a metal (aluminum, titanium, cast iron and thelike) but has a large chemical affinity with carbide cermet (carbon isan main ingredient). Therefore, a fluoride spray coating having anexcellent adhesion can be formed to a surface of the undercoat layer orthe primer part having a deposited layer of carbide cermet sprayparticles as a main ingredient due to a physical function itself or aphysical function combined with a chemical affinity function.(3) Since, in the undercoat layer and the primer part of carbide cermet,a part of primary spray particles is first stuck or embedded to thesubstrate surface and then they become gradually a film-shaped state, astrong compressive residual stress occurs in these substrates, and thusthe substrate exhibits a strong resistance to a deformation and astrain. In a member to which the treatment mentioned above is performed,a peeling-off of fluoride spray coating due to mechanical load andvibration of a member covered with a fluoride coating is suppressedduring an actual using environment.(4) In addition to the function and effect of the undercoat layer andthe primer part of carbide cermet, it is possible to obtain a memberhaving a strong adhesion of respective coatings mutually by forming afluoride spray coating under a condition that an overall substrate ispreheated.(5) Since, in the fluoride spray coating covered member according to theinvention, a firm adhesion between the substrate and the fluoride spraycoating through carbide cermet can be performed, the fluoride spraycoating body exhibits an excellent corrosion resistance (halogen gasresistance) and halogen gas plasma erosion resistance, and it ispossible to obtain a member which endures for a long time of use ifapplied to a semiconductor working member and the like.(6) Since the fluoride spray coating covered member according to theinvention has an undercoat layer and a primer part in which a tipportion of spraying particles is embedded in a substrate by stronglyspraying a hard carbide cermet particle such as WC—Ni—Cr and Cr₃C₂—Ni—Crinto a substrate surface with a high-velocity flame spaying method, itis possible to form a fluoride spray coating having a further strongadhesion on the substrate.

That is, since a fluoride itself has a small surface energy (Al, Ti, Feand the like) and a weak chemical wettability, a mutual bonding forcebetween fluoride particles or an adhesion between the substrate and thefluoride particle is small, and thus there is a nature that it issometimes peeled-off. In this point, according to the invention, since afluoride and a carbide cermet (carbon is a main ingredient) has a strongchemical affinity and a good wettability between them, it is possible toimprove a coating adhesion by utilizing their chemical affinity as wellas a physical adhesion mechanism of the fluoride spray particles ifinterposing the undercoat layer and the primer part of carbide cermet.

(7) Further, since the undercoat layer of carbide cermet is dense(porosity: 0.1-0.6%) and the primer part of carbide cermet has astructure that a spray particle of carbide cermet is stuck as poles andis sparsely upstanding, there is a function for strongly suppressing astrain and a deformation of the substrate. Therefore, a peeling-offphenomenon of the fluoride spray coating which is liable to occur by adeformation or a vibration of the substrate can be preventedeffectively.(8) As explained above, the fluoride spray coating formed by a techniqueaccording to the invention can endure a thermal shock due to arepetition of an abrupt temperature variation as well as a physicalvariation such as a load of micro-vibration and bending stress, and canexhibit an excellent chemical property of primary fluoride spray coatingfor a long time.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart showing a process sequence for carrying out themethod according to the invention.

FIG. 2 illustrates an initial layer of a substrate surface to whichWC-12 mass % Co cermet particles are sprayed sparsely by a high-velocityflame spraying method and a cross sectional SEM image of the sameportion: (a) is a view of surface sparsely sprayed with the carbidecermet particles; (b) is an enlarged view of the surface; and (c) is across sectional view of a substrate condition prior to forming anundercoat layer sprayed with carbide cermet particles.

EMBODIMENTS FOR CARRYING OUT THE INVENTION

An embodiment of the invention will be explained below with reference tothe accompanying drawings. FIG. 1 is a flowchart showing processsequence for carrying out the method according to the invention.Hereinafter, the invention will be explained according to this processsequence.

(1) Substrate

As a substrate usable in the invention is Al and its alloy, Ti and itsalloy, various alloy steels including stainless steel, carbon steel, Niand its alloy and so on. In addition, ceramic sintered materials such asoxide, nitride, carbide and silicide, sintered carbon, and organicpolymer materials such as plastics can be used.

(2) Pretreatment

The surface of the substrate is preferable to be pretreated according tooperation standard of ceramic sprayed coatings defined in JIS H9302. Forexample, after removing rusts and fats on the substrate surface, a blasttreatment for roughening is performed concurrently with a descale andthe like by blowing abrasive particles such as Al₂O₃ and SiC. Theroughness after the blast roughening treatment is preferable to be aboutRa: 0.05-0.74 μm and Rz: 0.09-2.0 μm.

(3) Formation of a Film-Shaped Undercoat Layer or a Non-Film ShapedPrimer Part of Carbide Cermet

a. Film-Shaped Undercoat Layer of Carbide Cermet

Carbide cermet material having a particle size of 5-80 μm is sprayed ata high velocity to a roughened substrate surface after a blast processwith a spray gun by means of a high-velocity flame spraying method or aninert gas spraying method. Accordingly, an operation, which forms astate such that at least a part of tip portions of spray particles isstuck and is embedded to the substrate surface and also a state suchthat another part of tip portions adheres and is deposited, is performedat plural times (not less than 6 times). In this manner, an undercoatlayer, wherein the carbide cermet is gradually made thicker and adheresin a film-shaped manner, is formed. This undercoat layer is formed in afilm-shaped state by spraying the carbide cermet material (particlesize: 5 μm-80 μm) at a spraying number of about not less than 6 timesand not more than 10 times by means of a spray gun for high velocityspraying with a flying velocity of 150-600 m/sec. and preferably 300-600m/sec. It should be noted that, if a flying velocity of the sprayingparticles is less than 150 μm, a bitten depth of the particles into thesubstrate surface is not sufficient and adhesion strength is decreased.On the other hand, when the flying velocity exceeds 600 m/sec., aneffect is saturated in the case of using the carbide cermet particles.Moreover, if the spraying number is not more than 5 times, it isdifficult to form a uniform film-shaped spray coating.

FIG. 2 shows forms of a substrate surface and a section thereof at aninitial state in the formation of the undercoat layer of carbide cermetmaterials i.e. just after the carbide cermet particles are sprayed at aflying velocity of 550 m/sec. by a high-velocity flame spraying method.FIG. 2( b) shows a state that a part of sprayed WC—Co cermet particlesadhere to a substrate surface so as to dig thereinto, while the otherWC—Co cermet particles are scattered in the substrate at a partiallycrushed state by collision energy and attached thereto. FIG. 2( c) showsa cross-sectional state when observing a distribution condition of WC—Cocermet particles sprayed to a surface layer portion of the substratesurface at an initial stage before the coating formation. As seen fromthis photograph, tip portions of part of WC—Co cermet particles arestuck and buried into the substrate surface at the initial stage whilethe other part becomes simply adhered or buried state. In this manner,more uniform coating is obtained as the spraying number is increased.

That is, when the WC—Co spraying material is sprayed further repeatedly(≧6 times) to the substrate surface adhered with WC—Co cermet sprayingparticles by a high-velocity flame spraying method, WC—Co particles aregradually deposited even onto a non-adhered parts of the substratesurface (black parts of FIG. 2( a)), to form a film-shaped undercoatlayer of WC—Co cermet particles applied over the whole surface in duecourse. On the contrary, in the case of general metallic undercoat ofNi—Cr, Ni—Al, or the like widely used in the formation of an oxideceramic spray coating, particles buried in the substrate as shown inFIG. 2 are not observed.

In the invention, when the undercoat layer of carbide cermet is formedin the substrate surface, the adhesion between the undercoat and thesubstrate is enhanced by the behavior of hard carbide cermet, while theimprovement of the adhesion of undercoat layer/topcoat (fluoride spraycoating) i.e. adhesion of the fluoride spray coating is attained by asynergistic effect of a surface roughness of the undercoat layer and achemical affinity between carbon and fluoride (top coat).

Carbide cermet spraying particles being at a state that the particlesexisting in a lowermost layer of the undercoat layer are stuck into thesubstrate surface are firmly bonded to the substrate while a largecompression strain is applied to the substrate surface, which not onlygives a large resistance to mechanical deformation of the substrate butalso improves the adhesion between the substrate and the undercoat layerof carbide cermet itself to improve the adhesion to the fluoride spraycoating covered thereon.

In the invention, the undercoat layer of carbide cermet adhered anddeposited onto the substrate surface at a state of burying a part of thespraying particles is particularly effective for the substrate beingsoft and susceptive to deformation or strain under a load in a useenvironment such as Al and its alloy, Ti and its alloy, mild steel,various stainless steels and so on, and guarantees the formation offluoride spray coating having always a stable and high adhesionregardless of kind of substrate material.

That is, a fluoride coating is originally poor in the ductility andsmall in the surface energy and hardly joins to a metal seriessubstrate, so that the peel-off of the coating is easily caused by thegeneration of a little deformation or strain of the substrate. However,it is possible to suppress external stress or a strain applied to thefluoride coating by the suppression of the substrate deformability dueto the burying of carbide cermet particles into the substrate surfaceand the formation of the undercoat layer of carbide cermet formedthereon.

The thickness of the undercoat layer of carbide cermet formed on thesubstrate surface is preferable within a range of 30-200 μm,particularly preferable within a range of 80-150 μm. When the thicknessof the undercoat layer is less than 30 μm, the coating thickness becomeseasily uneven, while when it exceeds 200 μm, an effect as the undercoatlayer is saturated and is uneconomic.

b. Formation of Non-Film Shaped Primer Part by Carbide Cermet

Carbide cermet particles having a particle size of 5-80 μm are sprayedonto the substrate surface which is roughened through blasting at a highvelocity by a spray gun for high-velocity spraying used in ahigh-velocity flame spraying method or an inert gas spraying method,whereby tip portions of at least a part of the sprayed hard carbidecermet particles are independently skewed and stuck as piles into thesubstrate surface. Moreover, according to this method, a portion (primerpart), in which the carbide cermet particles adhering to the substratesurface in a sparse pattern are dotted and adhere, is formed. In thiscase, if the particle size of the carbide cermet particles is less than5 μm, the amount supplied to a spray gun becomes uneven and the uniformspraying can not be performed. In addition, the amount of skewedparticles becomes small and it is impossible to form effective primerpart wherein spray particles are effectively dotted and adhered. On theother hand, if the particle size exceeds 80 μm, the skewing effectbecomes weakened.

Moreover, as is the same as the undercoat layer, the primer part is apart that the carbide cermet material (particle size 5-80 μm) is sprayedto the substrate surface at an area ratio of 8-50% with a spray gun at aflying velocity of 150-600 m/sec, preferably 300-600 m/sec in thespraying number of not more than 5 times, preferably not more than 3times to adhere the sprayed particles at a state of sparsely sticking aspiles.

The primer part, wherein carbide cermet spray particles dispersedsparsely in this treating step is dotted, is not completely film-shapedand forms the following structure. That is, as seen from FIGS. 2( a) and2(b) showing an appearance state when particles of WC-12 mass % Cocarbide cermet material are sprayed to a surface of SUS310 steelsubstrate, a part of the sprayed WC—Co cermet particles is at a state ofadhering to 8-50% portions of the substrate surface so as to digthereinto. Moreover, the other WC—Co cermet particles are dispersedlyadhered to the substrate surface at a state of being partially crushedby collision energy, and further a part of the other is at a state ofcompletely burying in the substrate to form a reinforcing layer ofcarbide cermet in the surface layer of the spray coating.

FIG. 2( c) is a view observing a distribution state of the sprayed WC—Cocermet particles existing in the surface layer portion of the substrateat section. As seen from this photograph, WC—Co cermet particles areexistent at a state of foresting small piles sparsely stuck in thesubstrate surface and another part thereof is simply adhered or buried.In the invention, when the fluoride particles are sprayed onto thesubstrate surface at such a state, i.e. onto the primer part (this partdoes not form a complete layer) of the carbide cermet particles adheredat such state, the fluoride spray coating having high adhesion will beformed by utilizing a mutual interlocking effect i.e. anchoring effect(JIS H8200 Thermal spraying terms) with hard WC—Co cermet particlesstuck as piles (fluoride spray particles) or a skewing phenomenon(fluoride particles are skewed and adhere to a tip portion of hard WC—Cocermet particle stuck as piles).

In this invention, as for a construction of the primer part of thecarbide cermet, an area ratio (area occupying ratio) of carbide cermetparticles is shown by means of an image analyzing device using SEMphotograph of FIG. 2( a) or FIG. 2( b) when white parts are carbidecermet particles and black parts are an exposed surface of thesubstrate. That is, in the primer part, a ratio occupied by the sprayparticles with respect to the surface area of the substrate i.e. an arearatio is to be controlled within a range of 8-50% preferably. This isbecause, when it is less than 8%, the wedging effect of carbide cermetparticles is weak, while when it exceeds 50%, the action mechanism isthe same as in an undercoat layer of carbide cermet mentioned later andthe wedging effect of the fluoride particles becomes small. In thisinvention, a state of the substrate surface in which the carbide cermetparticles are sprayed at an area ratio of 8-50% to the substrate surfaceis called as “primer part”.

As the carbide cermet spraying material usable in this invention can beused of WC—Co, WC—Ni—Cr, WC—Co—Cr, Cr₃C₂—Ni—Cr and the like. Moreover, apercentage of metal ingredient occupied in this carbide cermet ispreferably within a range of 5-40 mass %, particularly preferable withina range of 10-30 mass %. The reason is that if a metal ingredient isless than 5 mass %, the hard carbide is made to a small powder and aratio remaining on the substrate surface becomes small when spraying tothe substrate surface strongly. On the other hand, when the metalingredient exceeds 40 mass %, the hardness and corrosion resistance aredeteriorated and the entangling effect with the fluoride particle isdecreased, and the substrate is liable to be corroded by a corrosive gaspenetrated from through-holes of the fluoride spray coating and also thebonding force of the fluoride spray coating is vanished to induce thepeeling-off.

The sprayed carbide cermet material is preferred to have a particle sizeof 5-80 μm, particularly 10-45 When the particle size is less than 5 μm,the supply to the spray gun becomes discontinuous, and the formation ofuniform coating is difficult, and the particles are finely crushed andscattered in the collision with the substrate and hardly retains on thesubstrate surface. While, when the particle size exceeds 80 μm, aneffect is saturated and it is difficult to obtain commercially availableproducts.

(4) Preheating of Substrate

The substrate after the roughening and the substrate after the formationof the undercoat layer of carbide cermet and a primer part wherein sprayparticles are dotted are subjected to a preheating prior to the fluoridespraying treatment. The preheating temperature is preferable to becontrolled in accordance with the nature of the substrate and isrecommended to be the following temperature. Moreover, the preheatingmay be performed as one of pretreatments.

(i) Al, Ti and alloys thereof: 80° C.-250° C.(ii) Iron steel (low alloy steel): 80° C.-250° C.(iii) Stainless steels: 80° C.-250° C.(iv) Ceramic sintered material of oxides, carbides and the like: 120°C.-500° C.(v) Sintered carbon: 200° C.-700° C.

Moreover, the preheating may be conducted in air or under vacuum or inan inert gas, but an atmosphere of oxidizing the substrate material bypreheating to produce an oxide film on the surface should be avoided.

As a method for forming a fluoride spray coating, atmospheric plasmaspraying method, reduced-pressure plasma spraying method, high-velocityflame spraying method and the like are preferably used.

(5) Formation of Fluoride Spray Coating (Topcoat)

a. Fluoride Spraying Material

As a fluoride spraying material used in the invention are includedfluorides of Mg in Group Ha of the Periodic Table, Al in Group IIIb ofthe Periodic Table, Y in Group IIIa of the Periodic Table, andlanthanide metals belonging to Atomic Number 5771 in the Periodic Table.The metal elements of Atomic Number 5771 are 15 sorts of lanthanum (La),cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm),samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium(Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb) andlutetium (Lu).

As the fluoride spraying material are used fluoride particles of theabove metal adjusted to be a particle size of 5-80 μm. When the sprayingmaterial is a fine particles having a particle size of less than 5 μm,there is a drawback that the particles are frequently flied apartwithout forming the coating in the collision with the substrate surfacewhile when the particle size exceeds 80 μm, the rate supplied to aspraying gun is hardly equalized and the tendency of increasing the poresize of the formed coating becomes remarkable.

The spray coating by spraying fluoride spray materials formed on thesurface of the substrate or the like after the roughening or after theformation of the undercoat layer or primer part of carbide cermet orfurther the preheating is sufficient to have a thickness of 20-500 μm,particularly 50-200 μm is preferable. When the coating is thinner than20 μM, uniform thickness is not obtained, while when the thicknessexceeds 500 μm, residual stress in the formation of the fluoride coatingbecomes large to bring about the decrease of the adhesion force to thesubstrate and the peeling is liable to be easily caused.

b. Characteristics of Fluoride Spray Coating

As physicochemical properties of the fluoride itself can be pointed outthe followings. That is, the fluoride coating has a chemical stabilityto a halogen-based gas as compared with a metal coating or a ceramiccoating but is weak in the mutual bonding force of fluoride particlesconstituting the coating and adhesion strength to the substrate becausethe surface energy is small. Also, since a large residual stress isliable to be generated when forming a coating, a peeling-off of thecoating is liable to occur easily and frequently due to a slightdeformation of substrate after coating-formation. In addition, since thefluoride is poor in ductility, the coating is “cracked” easily andcauses corrosion of the substrate due to internal penetration of an acidor alkali cleaning liquid together with porous portions produced in theabove coating formation. Therefore, the fluoride is good in thecorrosion resistance but has a problem that the property cannot beutilized as a corrosion resistance coating.

In this regard, if the aforementioned of the invention is applied, sincethe undercoat layer or the primer part of carbide cermet is formed tothe substrate surface, adhesion of the coating is further improved,whereby the above problems of the fluoride spray coating can be solved.That is, the effect of preventing the corrosion of the substrate can beseen by the prevention from peeling or cracking of the coating and theprevention from penetration of the cleaning fluid accompanied therewith.

Moreover, the fluoride spray coating formed according to the inventioncan be used as is in a coating-forming state, but is subject to a heattreatment at 250° C.-500° C. after the coating formation, if necessary,whereby the residual stress can be released easily or an amorphous phasecan be easily crystallized (orthorhombic crystal phase). In theinvention, therefore, the use of these treatments is not particularlylimited. The reason why the temperature of the heat treatment is limitedto the above range is due to the fact that when it is lower than 250°C., a long time is taken for releasing the residual stress of thecoating and the crystallization is also insufficient, while when itexceeds 500° C., there is a possibility for promoting a physicochemicalchange of the fluoride spray coating.

EXAMPLES Example 1

In this example, an influence of pretreatment of a substrate surfaceaffected to an adhesion of fluoride spray coating is investigated.

(1) Kind of Pretreatment

The following pretreatments are performed to one surface of Al3003 alloy(“JIS M 4000”, size: diameter 25 mm×thickness 5 mm) as the substrate.

(i) After degreasing, the surface is polished by a wire brush lightly.(ii) After degreasing, a metal undercoat layer of Ni-20 mass % Cr havinga thickness of 50 μm is formed by an atmospheric plasma spraying method(flying velocity: 250 m/sec.).(iii) After degreasing, a primer part is formed by blowing WC-12 mass %Co in a sparse pattern (area ratio: 22%) by a high-velocity flamespraying method (flying velocity: 580 m/sec., spraying number: 3 times).(iv) After degreasing, an undercoat layer of carbide cermet of Cr₃C₂-18mass % Ni-7 mass % Cr having a thickness of 30 μm is formed by ahigh-velocity flame spraying method (flying velocity: 560 m/sec.,spraying number: 6 times).(v) After degreasing, a blast roughening treatment is performed to asubstrate surface by using Al₂O₃ abrasive.(vi) After the above blast roughening treatment, a metal undercoat layermade of Ni-20 mass % Cr film having a thickness of 50 μm is furtherformed by atmospheric plasma spraying method (same as (ii)).(vii) After the above blast roughening treatment, a primer part isfurther formed by blowing WC-12 mass % Co in a sparse pattern (arearatio: 18%) by a high-velocity flame spraying method (same as (iii)).(viii) After the above blast roughening treatment, an undercoat layer ofcarbide cermet having a thickness of 30 μm is further formed by blowingCr₃C₂-18 mass % Ni-7 mass % Cr by a high-velocity flame spraying method(same as (iv)).

(2) Formation of Fluoride Spray Coating

With respect to the substrate surface after the above pretreatments, YF₃spray coating having a thickness of 100 μm is formed by an atmosphericplasma spraying method.

(3) Test Method of Coating Adhesion

An adhesion of a coating is measured by a test method of adhesionstrength defined in Test method of ceramic spray coating of JIS H8666.

(4) Test Results

Test results are shown in Table 1. As is clear from these results, thesample piece (No. 1), in which a fluoride spray coating is formed afterdegreasing the substrate surface only, seldom indicates adhesion force,and the coating is peeled-off at 0.5-1.2 MPa. Moreover, the coating (No.2) formed on the metal undercoat layer indicates an adhesion force ofabout 4-5 MPa. However, since a blast roughening treatment is notperformed to the substrate surface, some sample pieces show apeeling-off from a boundary between the metal undercoat layer and thesubstrate. On the other hand, the sample piece (No. 3), in which theprimer part of carbide cermet particle is formed, and the sample piece(No. 4), in which the undercoat layer is formed, exhibit a high adhesionforce. Therefore, it is confirmed that, even if a blast rougheningtreatment is omitted, adhesion force required for an actual use can beobtained.

Then, since YF₃ coating (No. 5) formed on the blast roughened substratesurface indicates an adhesion force of 4-6 MPa and has a high bondingforce as compared with the coating of No. 1, it is confirmed that ablast roughening treatment is effective for a formation of fluoridespray coating. Moreover, an adhesion of the test pieces (Nos. 7 and 8),wherein a primer part or an undercoat layer is formed by sprayingcarbide cermet particles to a substrate surface, to which a blastroughening treatment is performed, and then a fluoride spray coating isformed thereon, is further increased. Therefore, it is confirmed thatthese treatments are suitable for the pretreatment method for forming afluoride spray coating.

TABLE 1 Coating Structure Adhesion No. Substrate Pretreatment UndercoatTopcoat MPa Remarks 1 Al3003 Degreasing None YF₃ 0.5~1.2 Comparative 2(Al Only Ni—Cr 4~5 example alloy) (Light wire (50 μm) 3 brushing)WC—12Co 13~16 Invention Blowing example (Primer part) 4 Cr₃C₂—Ni•Cr14~19 Invention (Undercoat example layer) (30 μm) 5 Blast treatment None4~6 Comparative 6 after Ni—Cr 7~8 example degreasing (50 μm) 7 WC—12Co13~15 Invention Blowing example (Primer part) 8 Cr₃C₂—Ni•Cr 14~18Invention (Undercoat example layer) (30 μm) (Remarks) (1) The coating tobe tested is formed by an atmospheric plasma spraying method and has athickness of 100 μm. (2) Three samples are tested per one condition andan adhesion force of coating is indicated by maximum value to minimumvalue. (3) The adhesion strength of the coating is measured by a testmethod defined at JIS H8666 Test method of ceramic sprayed coating.

Example 2

In this example, an adhesion of the spray coating is examined when YF₃spray coating having a thickness of 100 μm is formed to SS400 steelsubstrate by a reduced-pressure plasma spraying method.

(1) Kind of Pretreatment (Roughening, Formation of Intermediate Layer)

Pretreatments, that are the same kinds as those of Example 1, areperformed.

(2) Formation of Fluoride Spray Coating

A fluoride spray coating having a thickness of 100 μm is formed by aplasma spraying method (a reduced-pressure plasma spraying method) usingYF₃ under reduced pressure environment of Ar gas at 100-200 hPa.

(3) Test Method of Coating Adhesion

The same test method as that of Example 1 is performed.

(4) Test Results

Test results are shown in Table 2. As seen from the results, an adhesionof the coating after blast treatment is higher as compared with the case(No. 1) in which YF₃ spray coating is directly formed to the substratesurface, and it is confirmed that an excellent adhesion can be obtainedas compared with Al alloy substrate of Example 1. However, even if SS400steel substrate is used, the cases (Nos. 3 and 7) wherein the primerpart is formed by spraying carbide cermet particles and the cases (Nos.4 and 8) wherein the undercoat layer is formed exhibit further higheradhesion. That is, it is confirmed that the pretreatment method in whichthe undercoat layer and the primer part are formed by carbide cermet canalways form the coating having a high adhesion regardless of effects ofsubstrate kinds.

TABLE 2 Coating Structure Adhesion No. Substrate Pretreatment UndercoatTopcoat MPa Remarks 1 SS400 Degreasing None CeF₃ 0.7~1.3 Comparative 2steel Only Ni—Cr 4~5 example (Light wire (50 μm) 3 brushing) WC—12Co15~18 Invention Blowing example (Primer part) 4 Cr₃C₂—Ni•Cr 16~19Invention (Undercoat example layer) (30 μm) 5 Blast treatment None 5~8Comparative 6 after Ni—Cr 10~12 example degreasing (50 μm) 7 WC—12Co15~18 Invention Blowing example (Primer part) 8 Cr₃C₂—Ni•Cr 17~20Invention (Undercoat example layer) (30 μm) (Remarks) (1) The coating tobe tested is formed by a reduced-pressure plasma spraying method and hasa thickness of 100 μm. (2) Three sample pieces are tested per onecondition and an adhesion of coating is indicated by maximum value tominimum value. (3) The adhesion strength of the coating is measured by atest method defined at JIS H8666 Test methods for ceramic sprayedcoatings.

Example 3

In this example, an adhesion of YF₃ spray coating formed to SS400 steelsubstrate by a high-velocity flame spraying method is examined.

(1) Kind of Pretreatment (Roughening, Formation of Intermediate Layer)

Pretreatments, that are the same as those of Example 1, are performed.

(2) Formation of Fluoride Spray Coating

A fluoride spray coating having a thickness of 100 μm is formed by ahigh-velocity flame spraying method using YF₃.

(3) Test Method of Coating Adhesion

The same test method as that of Example 1 is performed.

(4) Test Results

Test results are shown in Table 3. As seen from the results of thistable, as is the same results as those of Examples 1 and 2, in the cases(Nos. 3, 4, 7, 8) wherein the undercoat layer and the primer part ofcarbide cermet are formed according to the invention, it is confirmedthat it is always possible to form a fluoride spray coating having ahigh adhesion regardless of presence or absence of a blast rougheningtreatment of the substrate.

TABLE 3 Coating structure Adhesion No. Substrate pretreatment UndercoatTopcoat MPa Remarks 1 SS400 Degreasing None YF₃ 0.6~1.3 Comparative 2steel Only Ni—Cr 3~4 example (Light wire (50 μm) 3 brushing) WC—12Co10~12 Invention Blowing example (Primer part) 4 Cr₃C₂—Ni•Cr 12~13Invention (Undercoat example layer) (30 μm) 5 Blast treatment None 2~4Comparative 6 after Ni—Cr 4~5 example degreasing (50 μm) 7 WC—12Co 11~14Invention Blowing example (Primer part) 8 Cr₃C₂—Ni•Cr 14~16 Invention(Undercoat example layer) (30 μm) (Remarks) (1) The coating to be testedis formed by a high-velocity flame spraying method and has a thicknessof 100 μm. (2) Three sample pieces are tested per one condition and anadhesion of coating is indicated by maximum value to minimum value. (3)The adhesion strength of the coating is measured by a test methoddefined at JIS H8666 Test methods of ceramic spray coatings.

Example 4

In this example, SUS304 steel is used as a substrate, and an adhesion ofthree kinds of fluoride spray coatings formed by an atmospheric plasmaspraying method is examined.

(1) Kind of Pretreatment

After a substrate is subjected to a blast roughening treatment by SiCabrasives, WC-12 mass % Co-5 mass % Cr or Cr₃C₂-17 mass % Ni-7 mass % Cris brown onto the roughened surface at a high-velocity as is the sameconditions of Example 1 so as to obtain a blowing thickness of 80 μm.

(2) Formation of Fluoride Spray Coating

A fluoride spray coating having a thickness of 120 μm is formed by anatmospheric plasma spraying method using CeF₃, DyF₃ and EuF₃.

(3) Test Method of Coating Adhesion

The same test method as that of Example 1 is performed.

(4) Test Results

Test results are shown in Table 4. As seen from the results of thistable, it is confirmed that the coating to which the undercoat layer ofcarbide cermet is formed has an effect for improving an adhesion to thefluoride spray coating such as CeF₃, DyF₃ and EuF₃.

TABLE 4 Adhesion according to pretreatment kind Blast WC—12CoCr₃C₂—Ni•Cr Coating roughening (Primer (Undercoat No. Substrate materialtreatment None part) layer) 1 SUS304 CeF₃ perform 4~7 11~12 11~14 2steel DyF₃ 5~8 10~14 12~15 3 EuF₃ 4~6 11~13 12~14 (Remarks) (1) Thecoating to be tested is formed by an atmospheric plasma spraying methodand has a thickness of 120 μm. (2) Three sample pieces are tested perone condition and an adhesion of coating is indicated by maximum valueto minimum value. (3) The adhesion strength of the coating is measuredby a method defined at JIS H8666 Test methods of ceramic sprayingcoatings.

Example 5

In this example, a primer part of carbide cermet and a fluoride spraycoating thereon are formed to a surface of Al alloy substrate (size:width 30 mm×longitudinal 50 mm×thickness 3 mm) by the method adapted tothe invention to evaluate a resistance to plasma etching of the spraycoating.

(1) Substrate: A fluoride spray coating is prepared by: subjecting asurface of Al alloy (A3003 defined by JIS H4000) to a blast rougheningtreatment; performing a pretreatment for forming a primer part having asparse pattern (area ratio of 12%) by blowing carbide cermet materials(spraying number: 2 times) at a high velocity (550 m/sec.) according tothe invention; and preheating at a temperature of 180° C.

(2) Fluoride for coating-formation: YF₃, DyF₃ and CeF₃ (particle size5-45 μm) are sprayed to form a coating having a coating thickness of 180μm by an atmospheric plasma spraying method. Moreover, as a coating of acomparative example, oxide coatings having a thickness of 180 μmrespectively, which are formed by the atmospheric plasma spraying methodof Y₂O₃, Dy₂O₃ and CeO₂, are tested.

(3) Gas Composition of Plasma Etching Atmosphere and Plasma Output

(i) Conditions of atmospheric gas and flow rate(a) F-containing gas: CHF₃/O₂/Ar=80/100/160 (flow rate per 1 minute cm³)(b) CH-containing gas: C₂H₂/Ar=80/100 (flow rate per 1 minute cm³)(ii) Plasma irradiation outputHigh-frequency power: 1300 W

Pressure: 4 Pa Temperature: 60° C.

(iii) Atmosphere of plasma etching test(a) Performed in a F-containing gas atmosphere(b) Performed in a CH-containing gas atmosphere(c) Performed in an alternately repeated atmosphere of F-containing gasatmosphere for 1 hour

CH-containing gas atmosphere for 1 hour

(4) Evaluation Method

In an evaluation of the test of plasma erosion resistance, the plasmaerosion resistance and environmental pollution resistance areinvestigated by measuring the number of particles of coating ingredientsflied from the coating to be tested by etching treatment. The number ofparticles is evaluated by measuring time duration until the number ofparticles having a particle size of not less than 0.2 μm adhered to asurface of silicon wafer having a diameter of 8 inch disposed in a testcontainer reached to 30.

(5) Test Results

Test results are shown in Table 5. As seen from the results, the oxidebased spray coatings (No. 1, 3, 5) of the comparative examples indicatesuch a situation that the generation of particles is smallest in theCH-containing gas and becomes somewhat large in the F-containing gas,and the time reaching to an acceptable value becomes short. However, itis proved that the number of particles generated becomes further largein the alternately repeated atmosphere of the F-containing gas and theCH-containing gas and the time reaching to an acceptable value becomesvery short. This cause is considered due to the fact that the oxide filmin the surface of the oxide ceramic coating becomes always unstable andis scattered by a repetition of oxidation function of fluoride gas inthe F-containing gas and a reduction function of CH gas. On the otherhand, it is considered that the fluoride spray coatings of No. 2, 4 and6 are maintained in a chemically stable state even in the F-containinggas, in the CH-containing gas and the alternately repeated atmosphere ofthese gasses, which is considered to suppress the generation ofparticles.

TABLE 5 Time until particle generation amount exceeds acceptable valueMutual repetition of Coating F CH gas containing to containingcontaining F and gas No. be tested gas gas containing CH Remarks 1 Y₂O₃70 120 35 Comparative example 2 YF₃ 108 220 82 Invention example 3 Dy₂O₃70 120 30 Comparative example 4 DyF₃ 98 210 77 Invention example 5 CeO₂80 78 30 Comparative example 6 CeF₂ 101 240 78 Invention example(Remarks) (1) Coating thickness of the coating to be tested is 180 μm.(2) Surface roughness of substrate after blast roughening treatment: Ra0.4-0.5 μm, Rz 0.7-1.0 μm. (3) Formation of coating is performed by anatmospheric plasma spraying method.

Example 6

In this example is examined a corrosion resistance to a vapor of ahalogen based acid in a fluoride spray coating formed on a substratesurface by a method adapted to the invention.

(1) Substrate: A substrate of SS400 steel (size: width 30mm×longitudinal 50 mm×thickness 3.2 mm) is used, and a coating-formationis performed by: subjecting a substrate surface to a blast rougheningtreatment; forming a primer part having a sparse pattern (area ratio of28%) of carbide cermet particles on the substrate surface by blowingcarbide cermet particles of Cr₂C₃-18 mass % Ni-8 mass % Cr at a highvelocity by a high-velocity flame spraying method (560 m/sec., sprayingnumber: 3 times); and preheating the substrate to a temperature of 200°C.

(2) Fluoride for coating-formation: MgF₂, YF₃ (particle size: 10-60 μm)are used, and a sample having a fluoride coating with a coatingthickness of 250 μm is prepared by a reduced-pressure plasma sprayingmethod. Moreover, as a coating of a comparative example, coatings havinga thickness of 250 μm respectively formed by a reduced-pressure plasmaspraying method of MgO, Y₂O₃, are tested under the same conditions.

(3) Corrosion Test

(a) A corrosion test by HCl vapor is adopted a method wherein 100 ml ofan aqueous solution of 30% HCl is placed in a bottom portion ofdesiccator for chemical experiment and a sample is suspended in a topportion thereof and exposed to HCl vapor generated from the aqueous HClsolution. A temperature of the corrosion test is 30° C.-50° C., and atime thereof is 96 hours.(b) A corrosion test by HF vapor is conducted by placing 100 ml of HFaqueous solution in a bottom portion of autoclave made of SUS316 andsuspending a sample in a top portion thereof. A temperature of thecorrosion test is 30° C.-50° C., and an exposing time thereof is 96hours.

(4) Test Results

Test results are shown in Table 6. As seen from the results, a largeamount of red rust reached to the surface of the coatings in the oxidebased coating of the comparative examples (No. 2, 4). That is, it isconsidered that, since many through-holes are existent in the oxidecoating, a vapor of HCl, HF and the like reaches to an interior of thecoating via the through-holes to corrode the SS400 steel substrate, andan iron component as a corroded product reaches to the coating surfacevia the through-holes to present red rust state. On the other hand, inthe fluoride coatings (No. 1, 3) formed according to the invention, ageneration of red rust is recognized, but its extent remained to about30-40% of the comparative example. From the results, it is found thatthere are through-holes in the fluoride spray coating but they arelittle as compared with those of the oxide spray coating, and furthersince the fluoride coating itself has an excellent corrosion resistance,the good corrosion resistance is developed to vapors of comprehensivehalogen based acids.

TABLE 6 Corrosion test results Coating HCl No. Substrate material vaporHF vapor Remarks 1 SS400 MgF₂ Δ Δ Invention example 2 steel MgO x xComparative example 3 YF₃ Δ Δ Invention example 4 Y₂O₃ x x Comparativeexample (Remarks) (1) The coating to be tested is formed to be athickness of 250 μm by a reduced-pressure plasma spraying method. (2) Anarea ratio of a sparse pattern by means of Cr₃C₂—Ni—Cr carbide particlesis 28%. (3) Symbols of corrosion test results: x: large generation ofred rust Δ: small generation of red rust.

INDUSTRIAL APPLICABILITY

The technique according to the invention can be applied to a surfacetreatment of members for precise working apparatus for semiconductorsrequiring a high resistance to halogen corrosion and plasma erosion. Forexample, they can be utilized as a corrosion resistant coating such asdeposit shield, baffle plate, focus ring, insulator ring, shield ring,bellows cover, electrode and the like disposed in a plasma treatingapparatus with a treating gas including halogen and a compound thereofas well as members for chemical plant apparatus in similar gasatmosphere.

Moreover, a technique for forming an undercoat layer of carbide cermetto a substrate according to the invention can be applied to a techniquefor processing a topcoat for metal (alloy) coating, oxide ceramics,plastics and the like.

1. A method for forming a fluoride spray coating characterized in thatan undercoat layer of carbide cermet, which covers a substrate in afilm-shaped manner while a tip portion of carbide cermet particles isembedded in the substrate, or a non-film shaped primer part of carbidecermet, is formed by blowing a carbide cermet material by using a spraygun for a high velocity spraying to the roughened substrate surface andafter that, a fluoride spray material is sprayed onto the undercoatlayer or the primer part.
 2. A method for forming a fluoride spraycoating according to claim 1, wherein the undercoat layer of carbidecermet is a layer with a film-shaped structure having a layer thicknessof 10 μm-150 μm, in which, at a side of a substrate surface, a tipportion of a part of the carbide cermet particles is embedded in thesubstrate and a thickness is made thicker by increasing a sprayingnumber.
 3. A method for forming a fluoride spray coating according toclaim 1, wherein the primer part of carbide cermet is made by a nonfilm-shaped structure having such a state that a tip portion of sprayparticles is stuck as piles and is sparsely upstanding, at a portion ofarea ratio 8-50% with respect to a substrate surface.
 4. A method forforming a fluoride spray coating according to claim 1, wherein theundercoat layer of carbide cermet and the primer part of carbide cermetare formed in such a manner that a spray treatment, in which particleshaving a particle size of 5-80 μm which is made of one or more metalcarbides selected from Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W and Si and 5-40mass % of one or more metals or their alloys selected from Co, Ni, Cr,Al and Mo are blown by using the spray gun for a high velocity blowingwhich can blow at a flying velocity of 150-600 m/sec., is repeated at 6times or more in case of the undercoat layer and at 5 times or less incase of the primer part.
 5. A method for forming a fluoride spraycoating according to claim 1, wherein the substrate is preheated to80-700° C. prior to a spraying fluoride particles.
 6. A method forforming a fluoride spray coating according to claim 1, wherein aspraying method of fluoride is any one spraying method selected fromatmospheric plasma spraying method, reduced-pressure plasma sprayingmethod and high-velocity flame spraying method.
 7. A method for forminga fluoride spray coating according to claim 1, wherein any of Al and itsalloy, Ti and its alloy, carbon steel, stainless steel, Ni and itsalloy, oxide, nitride, carbide, silicide, carbon sintered materials andplastics, a surface roughness of which is controlled to be Ra: 0.05-0.74μm and Rz: 0.09-2.0 μm by blowing abrasives such as Al₂O₃ and SiC with ablast roughening treatment, is used as the substrate.
 8. A method forforming a fluoride spray coating according to claim 1, wherein thefluoride spray coating is a coating by blowing fluoride particles havinga particle size of 5 μm-80 μm made of one or more selected fromfluorides of: Mg in Group IIa of the Periodic Table; Al in Group IIIb ofthe Periodic Table; Y in Group IIa of the Periodic Table; and lanthanideseries metals of Atomic Numbers 57-71 of the Periodic Table such as La,Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu onto thesubstrate surface at thickness of 20 μm-500 μm.
 9. A fluoride spraycoating covered member comprising: a substrate, a surface of which issubjected to a roughening treatment; a carbide cermet layer coated to asurface of the substrate; and a fluoride spray coating formed thereon,characterized in that the carbide cermet layer is a film-shapedundercoat layer wherein a part of carbide cermet particles is embeddedin the substrate to make a thickness thicker or a primer part ofnon-film shaped structure having a construction that a tip portion ofspray particles is stuck as piles and is sparsely upstanding, by blowingcarbide cermet particles having a particle size of 5-80 μm which is madeof one or more metal carbides selected from Ti, Zr, Hf, V, Nb, Cr, Mn, Wand Si and 5-40 mass % of one or more metals or their alloys selectedfrom Co, Ni, Cr, Al and Mo by using the spray gun for a high velocityblowing.
 10. A fluoride spray coating covered member according to claim9, wherein the undercoat layer of carbide cermet is a layer with afilm-shaped structure having a layer thickness of 10 μm-150 μm, inwhich, at a side of a substrate surface, a tip portion of a part of thecarbide cermet particles is embedded in the substrate and a thickness ismade thicker by increasing a spraying number.
 11. A fluoride spraycoating covered member according to claim 9, wherein the primer part ofcarbide cermet is made by a non-film shaped structure having such astate that a tip portion of spray particles is stuck as piles and issparsely upstanding, at an area ratio 8-50% with respect to thesubstrate surface.
 12. A fluoride spray coating covered member accordingto claim 9, wherein any of Al and its alloy, Ti and its alloy, carbonsteel, stainless steel, Ni and its alloy, oxide, nitride, carbide,silicide, carbon sintered materials and plastics, a surface roughness ofwhich is controlled to be Ra: 0.05-0.74 μm and Rz: 0.09-2.0 μm by aroughening treatment in which abrasives such as Al₂O₃ and SiC are blown,is used as the substrate.
 13. A fluoride spray coating covered memberaccording to claim 9, wherein the fluoride spray coating has a thicknessof 20-500 μm.
 14. A fluoride spray coating covered member according toclaim 9, wherein the fluoride spray coating is formed in such a mannerthat fluoride particles having a particle size of 5 μm-80 μm made of afluoride of one or more materials selected from a group of Mg in GroupIIa of the Periodic Table; Al in Group IIIb of the Periodic Table; Y inGroup IIIa of the Periodic Table; and lanthanide metals in AtomicNumbers 57-71 of the Periodic Table such as La, Ce, Pr, Nd, Pm, Sm, Eu,Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu are blown to the substrate surface tobe a coating thickness of 20 μm-500 μm.